The angiotensin receptor/neprilysin inhibitor Sacubitril/Valsartan (Sac/Val) has been shown to be beneficial in patients suffering from heart failure with reduced ejection fraction (HFrEF). However, the impact of Sac/Val in patients presenting with heart failure with preserved ejection fraction (HFpEF) is not yet clearly resolved. The present study aimed to reveal the influence of the drug on the functionality of the myocardium, the skeletal muscle, and the vasculature in a rat model of HFpEF. Female obese ZSF-1 rats received Sac/Val as a daily oral gavage for 12 weeks. Left ventricle (LV) function was assessed every four weeks using echocardiography. Prior to organ removal, invasive hemodynamic measurements were performed in both ventricles. Vascular function of the carotid artery and skeletal muscle function were monitored. Sac/Val treatment reduced E/é ratios, left ventricular end diastolic pressure (LVEDP) and myocardial stiffness as well as myocardial fibrosis and heart weight compared to the obese control group. Sac/Val slightly improved endothelial function in the carotid artery but had no impact on skeletal muscle function. Our results demonstrate striking effects of Sac/Val on the myocardial structure and function in a rat model of HFpEF. While vasodilation was slightly improved, functionality of the skeletal muscle remained unaffected.

Besides structural alterations in the myocardium, heart failure with preserved ejection fraction (HFpEF) is also associated with molecular and physiological alterations of the peripheral skeletal muscles (SKM) contributing to exercise intolerance often seen in HFpEF patients. Recently, the use of Sodium-Glucose-Transporter 2 inhibitors (SGLT2i) in clinical studies provided evidence for a significant reduction in the combined risk of cardiovascular death or hospitalization for HFpEF. The present study aimed to further elucidate the impact of Empagliflozin (Empa) on: (1) SKM function and metabolism and (2) mitochondrial function in an established HFpEF rat model. At the age of 24 weeks, obese ZSF1 rats were randomized either receiving standard care or Empa in the drinking water. ZSF1 lean animals served as healthy controls. After 8 weeks of treatment, echocardiography and SKM contractility were performed. Mitochondrial function was assessed in saponin skinned fibers and SKM tissue was snap frozen for molecular analyses. HFpEF was evident in the obese animals when compared to lean—increased E/é and preserved left ventricular ejection fraction. Empa treatment significantly improved E/é and resulted in improved SKM contractility with reduced intramuscular lipid content. Better mitochondrial function (mainly in complex IV) with only minor modulation of atrophy-related proteins was seen after Empa treatment. The results clearly documented a beneficial effect of Empa on SKM function in the present HFpEF model. These effects were accompanied by positive effects on mitochondrial function possibly modulating SKM function.

Aortic valve sclerosis is characterized as the thickening of the aortic valve without obstruction of the left ventricular outflow. It has a prevalence of 30% in people over 65 years old. Aortic valve sclerosis represents a cardiovascular risk marker because it may progress to moderate or severe aortic valve stenosis. Thus, the early recognition and management of aortic valve sclerosis are of cardinal importance. We examined the aortic valve geometry and structure from healthy C57Bl6 wild type and age-matched hyperlipidemic ApoE^−/− mice with aortic valve sclerosis using optical coherence tomography (OCT) and multiphoton microscopy (MPM) and compared results with histological analyses. Early fibrotic thickening, especially in the tip region of the native aortic valve leaflets from the ApoE^−/− mice, was detectable in a precise spatial resolution using OCT. Evaluation of the second harmonic generation signal using MPM demonstrated that collagen content decreased in all aortic valve leaflet regions in the ApoE^−/− mice. Lipid droplets and cholesterol crystals were detected using coherent anti-Stokes Raman scattering in the tissue from the ApoE^−/− mice. Here, we demonstrated that OCT and MPM, which are fast and precise contactless imaging approaches, are suitable for defining early morphological and structural alterations of sclerotic murine aortic valves.

Endovascular repair (EVAR) has become the standard procedure in treating thoracic (TAA) or abdominal aortic aneurysms (AAA). Not entirely free of complications, a persisting perfusion of the aneurysm after EVAR, called Endoleak (EL), leads to reintervention and risk of secondary rupture. How the aortic wall responds to the implantation of a stentgraft and EL is mostly uncertain. We present a pilot study to identify peptide signatures and gain new insights in pathophysiological alterations of the aortic wall after EVAR using matrix-assisted laser desorption or ionization mass spectrometry imaging (MALDI-MSI). In course of or accompanying an open aortic repair, tissue sections from 15 patients (TAA = 5, AAA = 5, EVAR = 5) were collected. Regions of interest (tunica media and tunica adventitia) were defined and univariate (receiver operating characteristic analysis) statistical analysis for subgroup comparison was used. This proof-of-concept study demonstrates that MALDI-MSI is feasible to identify discriminatory peptide signatures separating TAA, AAA and EVAR. Decreased intensity distributions for actin, tropomyosin, and troponin after EVAR suggest impaired contractility in vascular smooth muscle cells. Furthermore, inability to provide energy caused by impaired respiratory chain function and continuous degradation of extracellular matrix components (collagen) might support aortic wall destabilization. In case of EL after EVAR, this mechanism may result in a weakened aortic wall with lacking ability to react on reinstating pulsatile blood flow.

Pathological ECM remodelling and biomineralization in human aortic valve and bioprosthesis tissue were investigated by Fourier transformed infrared (FT-IR) spectroscopic imaging and multivariate data analysis. Results of histological von Kossa staining to monitor hydroxyapatite biomineralization correlated to the definition of mineralized tissue using FT-IR spectroscopic imaging. Spectra exhibit signals of carbonate and phosphate groups of hydroxyapatite. Proteins could be identified by the amide I and amide II bands. Proteins were detected in the calcified human aortic valve tissue, but no absorption signals of proteins were observed in the mineralized bioprosthesis sample region. A shift of the amide I band from 1654 cm⁻¹ to 1636 cm⁻¹ was assumed to result from β-sheet structures. This band shift was observed in regions where the mineralization process had been identified but also in non-mineralized bioprosthesis tissue independent of prior implantation. The increased occurrence of β-sheet conformation is hypothesized to be a promoter of the biomineralization process. FT-IR spectroscopic imaging offers a wealth of chemical information. For example, slight variations in band position and intensity allow investigation of heterogeneity across aortic valve tissue sections. The exact evaluation of these properties and correlation with conventional histological staining techniques give insights into aortic valve tissue remodelling and calcific pathogenesis.

BACKGROUND: Heart valves are exposed to a highly dynamic environment and underlie high tensile and shear forces during opening and closing. Therefore, analysis of mechanical performance of novel heart valve bioprostheses materials, like SULEEI-treated bovine pericardium, is essential and usually carried out by uniaxial tensile tests. Nevertheless, major drawbacks are the unidirectional strain, which does not reflect the in vivo condition and the deformation of the sample material. An alternative approach for measurement of biomechanical properties is offered by Brillouin confocal microscopy (BCM), a novel, non-invasive and three-dimensional method based on the interaction of light with acoustic waves. OBJECTIVE: BCM is a powerful tool to determine viscoelastic tissue properties and is, for the first time, applied to characterize novel biological graft materials, such as SULEEI-treated bovine pericardium. Therefore, the method has to be validated as a non-invasive alternative to conventional uniaxial tensile tests. METHODS: Vibratome sections of SULEEI-treated bovine pericardium (decellularized, riboflavin/UV-cross-linked and low-energy electron irradiated) as well as native and GA-fixed controls (n = 3) were analyzed by BCM. In addition, uniaxial tensile tests were performed on equivalent tissue samples and Young’s modulus as well as length of toe region were analyzed from stress-strain diagrams. The structure of the extracellular matrix (ECM), especially collagen and elastin, was investigated by multiphoton microscopy (MPM). RESULTS: SULEEI-treated pericardium exhibited a significantly higher Brillouin shift and hence higher tissue stiffness in comparison to native and GA-fixed controls (native: 5.6±0.2 GHz; GA: 5.5±0.1 GHz; SULEEI: 6.3±0.1 GHz; n = 3, p < 0.0001). Similarly, a significantly higher Young’s modulus was detected in SULEEI-treated pericardia in comparison to native tissue (native: 30.0±10.4 MPa; GA: 31.8±10.7 MPa; SULEEI: 42.1±7.0 MPa; n = 3, p = 0.027). Native pericardia showed wavy and non-directional collagen fibers as well as thin, linear elastin fibers generating a loose matrix. The fibers of GA-fixed and SULEEI-treated pericardium were aligned in one direction, whereat the SULEEI-sample exhibited a much denser matrix. CONCLUSION: BCM is an innovative and non-invasive method to analyze elastic properties of novel pericardial graft materials with special mechanical requirements, like heart valve bioprostheses.